Object does not show when pasted into scene
When the mesh is imported from another blend, - either linked or appended, it is placed on the same 3D Layer where it was in the original file.

To see whether there is something on any layer, look at the layers tab:



Layer 1 is selected, while both - 1-st and 2-nd have dot in the middle of the small rectangle.

This dot is orange - currently active object is located on that layer.
This dot is grey - there is/are some objects on that layer.

To show the mesh located on another layer, either Shift click on that rectangle, or press Shift + number of adjacent layer (in this case 2-nd). The mesh will be shown.